make compatible with xDripG5

[thebookins]

This PR is an attempt to make xDripAPS compatible with LoopKit/xDripG5 using Loop to upload local BGL data to the microservice exposed by the Edison.

Besides trivial changes to tabbing etc, this PR

• allows for multiple entries in the POST json data
• allows for optional keys in the posted entries ('filtered', 'unfiltered', 'rssi', 'noise')
• makes the POST command return a dict of entries that were successfully added, as per NS
• adds the endpoint '/api/v1/experiments/test', which Loop uses to check authentication

Every attempt has been made to leave the behaviour unchanged for existing users of xDrip+.